As friends growing up in Gaithersburg, Sahil Rahman and Rahul Vinod knew the best way to deal with skeptics of the food they loved — their non-Indian friends who believed Indian cuisine to be “just curry” or “too spicy” — was to take them to one of their fathers’ restaurants, Bombay Bistro in Rockville or Indique in Washington. Invariably, recalls Vinod, “they would love” the food and end up returning with their families in tow.

As young adults living in New York, where Rahman worked as a consultant and Vinod as an investment banker, the friends got serious about opening something fast and casual of their own. Three years ago, they relocated to Washington, where they helped their dads breathe new life into Indique and finessed their plans. In December, the entrepreneurs debuted Rasa, on a block in the Navy Yard where the competitors include such well-known brands as Cava, Taylor Gourmet and Roti Modern Mediterranean.

The drill will be familiar to bowl-builders at Sweetgreen, among the owners’ homegrown inspirations, while the look channels the richness (and quirks) of a country of 1.3 billion people. From the street, the big teak door, a statement in turquoise, makes an arresting first impression. For Rasa, Vinod and Rahman, both 27, got a design assist from Rahman’s aunt, artist Nandita Madan.

There’s more to like inside Rasa, which translates from Sanskrit to “essence” and captures the nine essential human emotions, called navarasa, in vivid color on canvasses lining the path to the food counter. I’ve never been to Rasa without seeing one of the two owners on the assembly line, assisting customers with their orders, or in the dining room, chatting up diners or offering them a taste of something they want them to try. One day brought saffron-tinted Indian yogurt, subtly sweet, delicately tangy and swirled with pistachios. Sold!

While customers are free to design their own meals from among scores of bases, sauces and toppings, some displayed in colorful Le Creuset pots, Rasa offers six compositions for inspiration. Their names alone elicit a smile. “Tikka Chance on Me” rewards the buyer with a scoop of basmati rice and nuggets of moist chicken to which a host of enhancements are added: pickled radishes, sauteed spinach, a drizzle of cumin-flavored yogurt and minty cilantro chutney. “Aloo Need Is Love” stars chunks of mellow sweet potato, glossy eggplant and a base of “supergrains” finished with a spicy coconut-ginger sauce. (The grains include ragi, or finger millet, which lends a subtle chocolate note to the dish.) Before a blue resin bowl is passed to customers, a sail of lentil crisp is tucked inside.

It might be fast and casual, but a lot of effort goes into this food. Almost everything is made from scratch, including garam masala, whose ingredients go through a spice grinder the business partners picked up in India. Family recipes account for some of the enticements; Rasa’s tamarind-coconut powder, using roasted fresh coconut, comes from Vinod’s grandmother, who was asked to sign off on the accent before the owners served it. While the sweet-tart condiment can be used on any bowl, Vinod says it was designed for the deliciously nuanced “Home Cooking,” thin rice noodles and gingery shrimp that share their bowl with wrinkly green beans, mango salsa and mango coconut yogurt.

Beef on the menu is a curiosity; Hindus, who make up almost 80 percent of India’s population, don’t eat the meat. Rahman says he identifies as much with his American experience as with his Indian heritage and points out that in Kerala, where his business partner’s father is from, Syrian Christians consume beef, famously in a beef fry. The slow-cooked, tongue-numbing meat at Rasa is dynamite, a beneficiary of a marinade sparked with curry leaves, tellicherry peppercorns and green chilies, then garam masala in follow-up seasoning.

The bookends to a meal include a rousing pumpkin soup, rich with coconut milk and faintly crunchy with pumpkin seeds; flaky, one-bite vegetable samosas; garlic naan that’s best followed with a breath mint; and, on the sweeter side, a loose-textured version of kulfi, India’s pleasantly chewy ice cream, charmingly presented as a push-up pop.

Beverages shine, too. Mango lassi, thick and creamy, is an expected presence. Rasa also offers house-made juices, wine (rosé in a can) and a gin and tonic that relies on local Green Hat gin, cinchona bark (to release the quinine found in tonic water) and a pantry of warm spices. You can smell the drink before you taste it.

Quibbles take work to find. Spiced tea tastes thin. And as much as I dig the cooked spinach, it needs to be drained before going into a bowl; excess water dilutes the other flavors.

The biggest hurdle to opening may have been training newbies to Indian food — jackfruit, among other ingredients, has yet to reach household name recognition — although the servers behind the line come across as well-versed.

You can take your food out, of course, but every time I’ve pondered doing so, the setting has compelled me to enjoy it then and there.

The interior, executed by the District design firm HapstakDemetriou+, deftly fuses whimsy with comfort. Near the front window hang comfy basket swings. Opposite the colorful painted navarasa are open-sided boxes, arranged as if falling onto each other and containing cookbooks, Indian hand drums and even Rahman’s grandfather’s lunch pail. (Rahman jokes that his bedroom is bare as a result of the display.) The “wave” of the boxes is cleverly repeated in the serpentine curves of the banquette. Even the ceiling, crisscrossed with colorful string, catches eyes.

Can we expect more Rasas in our future?

“We’re not looking ahead,” Rahman says, but trying to enjoy the moment and “working to make our guests happy.”

Good answer for residents of the Navy Yard, but if the evangelists ever want to expand their mission, this early convert will be cheering them on.